"Part One"

We first copied the original bridge apron and cap using "conventional" procedures--removing the entire bridge assembly, making a new apron and bridge using mylar templates, and re-installing the completed bridge onto the soundboard with glue and screws.

A – In evaluating the condition of a bass bridge, we look for FOUR things. First: Are all pins firmly in place so they can function well, or are any loose or missing? After examining this bass bridge, we concluded that we should at least recap it. In addition, we noticed that the "apron" was badly cracked and should be replaced.

B – Second: Is there sufficient downbearing, so that the strings exert adequate downward pressure onto the bridge, enabling it to transfer vibrations from the strings to the soundboard, thus producing good piano tone? We test downbearing by using a special device that shows percentage points of angular change in the strings at the front and the back of the bridge cap. Another way to measure downbearing is to extend a 4-foot straight edge from the plate pins over the bridge and check if the other end of the straight edge rises over the strings at the upper bridge.

C – Third: Are the strings all seated at both front and back edges of the bass bridge? If not, the piano may not produce good tone because of lost energy between the strings and the soundboard.

D – Fourth: Is the "cross-bearing" pattern of the strings consistent from the top string to the bottom string? Strings that are too straight may vibrate independently, and strings that have too great an angle over the bridge may cause the bridge pins to loosen.

E – We produced two "templates" of the bridge cap: one on paper and one on transparent mylar plastic.

F – We removed the soundboard buttons and screws that held down the bass bridge assembly.

G – We carefully removed the bridge assembly from the soundboard with chisels.

H – We made a new "apron" and bass bridge cap, copying the shape, size, and pin locations of the originals--assuming that they were correct.

I – We applied two coats of sealer to the new bridge before installing it.

J – We installed the new bass bridge using new screws and soundboard buttons.

"Part Two"

After restringing the piano and "chipping up to pitch," we checked for the four conditions mentioned above. (1) We found that the bridge pins and the "apron" of the new bass bridge were solidly installed. (2) However, we discovered that the treble strings exerted so much downward pressure on the soundboard that the bass bridge that we had installed was at least 1/8" too low. (3) We found that the top surface of the new bridge cap was not angled in the same direction as the strings. (4) We found that the cross-bearing pattern of the strings was inconsistent because our template, based on the original bridge cap, was inaccurate.

We were reluctant to remove the entire bridge assembly from the soundboard again--by now, the glue joint holding it to the soundboard was dry and any attempt to remove it would no doubt cause considerable damage to the soundboard. We decided to remove only the poorly constructed bridge cap and replace it with a better one.

1 – We cut a new cap the same shape as the original cap; then we made the surrounding "capping material" into a router jig the right height to place over the current bridge. We also drew a template on a piece of mylar plastic, to show the general direction of the strings. Clearly, the bridge we made in "Part One" had insufficient "cross-bearing" for most strings, because we had misjudged the location of the pins that had been located in cracks.

2 – With a small mirror, we located the screws supporting the bridge cap to the apron from the underside of the apron, made two cuts with a Japanese edging saw about 1/4" apart on both sides of each screw; and removed the wood around each screw with a narrow chisel in order to expose each screw tip.

3 – With the router jig in place wedged tightly between the arms of the piano plate at an angle parallel to the direction of the strings, we removed 3/8" thickness of wood from the old cap.

4 – We carefully avoided each screw in the routering process. We then chiseled away the wood remaining around each screw.

5 – We used an air-compressed die grinder and a dremel tool to grind each screw tip below the surface of the wood.

6 – Using a 4-ft. straightedge, we measured the downbearing with the bridge cap blank in place: the straightedge extended from the hitch pins to about 1/4" above the upper bridge, throughout the length of the bridge cap blank.

7 – We re-installed the strings, tightening them until they formed straight parallel lines over the bridge cap blank.

8 – We drilled two holes through the bridge cap part way into the "apron" and inserted two hammer shanks to position it; then we marked and drilled holes to the left of each string.

9 – For drilling bridge pin holes, we selected drill bits with diameter about .010" less than the diameter of the pins.

10 – With round tooth picks inserted in the holes already drilled, we marked and drilled the upper set of holes, just left of each string.

11 – We removed the hammer shanks and the new bridge cap.

12 – We sanded the two edges of the bridge with a rotary sander, then touched up with a dremel-tool sander, ensuring that each angled edge stops at the line of holes.

13 – We applied graphite to the top surface of the bridge cap and shellac to the beveled edges.

14 – We brushed glue onto both surfaces.

15 – With two pieces of wood dowel separating the bass and the cap, we pulled the new bridge cap into position; then we removed the dowels and positioned the bridge cap on the apron.

16 – We cut two pieces of hammer shank, painted one end with graphite, installed glue, and drove the hammer shanks into the positioning holes.

17 – We clamped the bridge cap to the apron for a couple of hours.

18 – With a piece of wood separating the strings, we drove in one row of bridge pins.

19 – Holding each string away from the hole with a string hook, we drove in the second row of bridge pins.

20 – We lightly sanded the tips of all the pins until all were the same height.

20 – We "chipped" the strings to pitch and installed stringing braid. DONE!

21 – We tested the new bridge for downbearing--the straight edge lay flat on the surface of the cap and extended to about 1/4" over the tops of the bass strings. Also, we obtained positive downbearing readings on both edges of the cap.

22 – We tested the seating of each string under each angled bridge pin--front and back--and found that all strings were pressed firmly across the top of the bridge cap.

23 – We checked the "cross-bearing" of the strings for consistency. We tested the tone by plucking the strings. We found that the tone of the bass section of this piano was richer and deeper as a result of the improvements in the bridge. The final test will of course be after action reconditioning and regulating has been completed, but we're confident that our extra effort will be rewarded!